Method for de-configuring a SCell from PUCCH resource in a carrier aggregation system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for de-configuring a cell from PUCCH resource in a carrier aggregation system, the method comprising: configuring a Secondary Cell (SCell) with Physical Uplink Control Channel (PUCCH) resource; receiving a signaling indicating that the PUCCH resource is de-configured from the SCell; de-configuring the PUCCH resource from the SCell according to the signaling; and triggering a Power Headroom Reporting (PHR) when the PUCCH resource is de-configured from the SCell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2016/000289, filed on Jan. 12, 2016,which claims the benefit of U.S. Provisional Application No. 62/103,032,filed on Jan. 13, 2015 and 62/188,494, filed on Jul. 3, 2015, thecontents of which are all hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system and,more particularly, to a method for de-configuring a SCell from PUCCHresource in a carrier aggregation system and a device therefor.

BACKGROUND ART

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

DISCLOSURE Technical Problem

An object of the present invention devised to solve the problem lies ina method and device for de-configuring a SCell from PUCCH resource in acarrier aggregation system. The technical problems solved by the presentinvention are not limited to the above technical problems and thoseskilled in the art may understand other technical problems from thefollowing description.

Technical Solution

The object of the present invention can be achieved by providing amethod for a UE operating in a wireless communication system, the methodcomprising: configuring a Secondary Cell (SCell) with Physical UplinkControl Channel (PUCCH) resource; receiving a signaling indicating thatthe PUCCH resource is de-configured from the SCell; de-configuring thePUCCH resource from the SCell according to the signaling; and triggeringa Power Headroom Reporting (PHR) when the PUCCH resource isde-configured from the SCell.

In another aspect of the present invention provided herein is anapparatus in the wireless communication system, the apparatuscomprising: an RF (radio frequency) module; and a processor configuredto control the RF module, wherein the processor is configured toconfigure a Secondary Cell (SCell) with Physical Uplink Control Channel(PUCCH) resource, to receive a signaling indicating that the PUCCHresource is de-configured from the SCell, to de-configure the PUCCHresource from the SCell according to the signaling, and to trigger aPower Headroom Reporting (PHR) when the PUCCH resource is de-configuredfrom the SCell.

Preferably, when the PUCCH resource is de-configured from the SCell, ifthe SCell is in activate state, the UE triggers the PHR.

Preferably, after the PUCCH resource is de-configured from the SCell, ifthe SCell is in activate state, the UE triggers the PHR.

Preferably, the signaling indicating that the PUCCH resource isde-configured from the SCell including at least one of: an indication ofthe SCell from which the PUCCH resource is de-configured; an indicationof PUCCH resource de-configuration of the SCell from which the PUCCHresource is de-configured.

Preferably, the signaling is received via a Radio Resource Control (RRC)or a Medium Access Control (MAC) signaling.

Preferably, the SCell from which the PUCCH resource is de-configured iseither activated or deactivated after the PUCCH de-configurationdepending on configuration.

Preferably, the method further comprises: transmitting the triggered PHRto a base station.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

According to the present invention, de-configuring a SCell from PUCCHresource can be efficiently performed in a carrier aggregation system.Specifically, a UE, configured with at least one SCell with PUCCHresource, triggers a PHR when the PUCCH resource is deconfigured fromone of the SCell.

It will be appreciated by persons skilled in the art that the effectsachieved by the present invention are not limited to what has beenparticularly described hereinabove and other advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2a is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2b is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention;

FIG. 6 is a diagram for carrier aggregation;

FIG. 7 is a conceptual diagram for Dual Connectivity (DC) between aMaster Cell Group (MCS) and a Secondary Cell Group (SCG);

FIG. 8 is a diagram for MAC structure overview in a UE side;

FIG. 9 is a diagram for an activation/deactivation MAC control element;and

FIG. 10 is a diagram for signaling of buffer status and power-headroomreports; and

FIG. 11 is a conceptual diagram for de-configuring a SCell with PUCCHresource in a carrier aggregation system according to embodiments of thepresent invention.

BEST MODE

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2a is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2a , the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2b is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2b , an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor(110) and RF module (transceiver; 135). The DSP/microprocessor (110) iselectrically connected with the transceiver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

Recently, Proximity-based Service (ProSe) has been discussed in 3GPP.The ProSe enables different UEs to be connected (directly) each other(after appropriate procedure(s), such as authentication), through eNBonly (but not further through Serving Gateway (SGW)/Packet Data NetworkGateway (PDN-GW, PGW)), or through SGW/PGW. Thus, using the ProSe,device to device direct communication can be provided, and it isexpected that every devices will be connected with ubiquitousconnectivity. Direct communication between devices in a near distancecan lessen the load of network. Recently, proximity-based social networkservices have come to public attention, and new kinds of proximity-basedapplications can be emerged and may create new business market andrevenue. For the first step, public safety and critical communicationare required in the market. Group communication is also one of keycomponents in the public safety system. Required functionalities are:Discovery based on proximity, Direct path communication, and Managementof group communications.

Use cases and scenarios are for example: i) Commercial/social use, ii)Network offloading, iii) Public Safety, iv) Integration of currentinfrastructure services, to assure the consistency of the userexperience including reachability and mobility aspects, and v) PublicSafety, in case of absence of EUTRAN coverage (subject to regionalregulation and operator policy, and limited to specific public-safetydesignated frequency bands and terminals).

FIG. 6 is a diagram for carrier aggregation.

Carrier Aggregation (CA) technology for supporting multiple carriers isdescribed with reference to FIG. 6 as follows. As mentioned in theforegoing description, it may be able to support system bandwidth up tomaximum 100 MHz in a manner of bundling maximum 5 carriers (componentcarriers: CCs) of bandwidth unit (e.g., 20 MHz) defined in a legacywireless communication system (e.g., LTE system) by carrier aggregation.Component carriers used for carrier aggregation may be equal to ordifferent from each other in bandwidth size. And, each of the componentcarriers may have a different frequency band (or center frequency). Thecomponent carriers may exist on contiguous frequency bands. Yet,component carriers existing on non-contiguous frequency bands may beused for carrier aggregation as well. In the carrier aggregationtechnology, bandwidth sizes of uplink and downlink may be allocatedsymmetrically or asymmetrically.

When CA is configured, the UE only has one RRC connection with thenetwork. At RRC connection establishment/re-establishment/handover, oneserving cell provides the NAS mobility information (e.g. TAI), and atRRC connection re-establishment/handover, one serving cell provides thesecurity input. This cell is referred to as the Primary Cell (PCell). Inthe downlink, the carrier corresponding to the PCell is the DownlinkPrimary Component Carrier (DL PCC) while in the uplink it is the UplinkPrimary Component Carrier (UL PCC).

Depending on UE capabilities, Secondary Cells (SCells) can be configuredto form together with the PCell a set of serving cells. In the downlink,the carrier corresponding to an SCell is a Downlink Secondary ComponentCarrier (DL SCC) while in the uplink it is an Uplink Secondary ComponentCarrier (UL SCC).

The primary component carrier is the carrier used by a base station toexchange traffic and control signaling with a user equipment. In thiscase, the control signaling may include addition of component carrier,setting for primary component carrier, uplink (UL) grant, downlink (DL)assignment and the like. Although a base station may be able to use aplurality of component carriers, a user equipment belonging to thecorresponding base station may be set to have one primary componentcarrier only. If a user equipment operates in a single carrier mode, theprimary component carrier is used. Hence, in order to be independentlyused, the primary component carrier should be set to meet allrequirements for the data and control signaling exchange between a basestation and a user equipment.

Meanwhile, the secondary component carrier may include an additionalcomponent carrier that can be activated or deactivated in accordancewith a required size of transceived data. The secondary componentcarrier may be set to be used only in accordance with a specific commandand rule received from a base station. In order to support an additionalbandwidth, the secondary component carrier may be set to be usedtogether with the primary component carrier. Through an activatedcomponent carrier, such a control signal as a UL grant, a DL assignmentand the like can be received by a user equipment from a base station.Through an activated component carrier, such a control signal in UL as achannel quality indicator (CQI), a precoding matrix index (PMI), a rankindicator (RI), a sounding reference signal (SRS) and the like can betransmitted to a base station from a user equipment.

Resource allocation to a user equipment can have a range of a primarycomponent carrier and a plurality of secondary component carriers. In amulti-carrier aggregation mode, based on a system load (i.e.,static/dynamic load balancing), a peak data rate or a service qualityrequirement, a system may be able to allocate secondary componentcarriers to DL and/or UL asymmetrically. In using the carrieraggregation technology, the setting of the component carriers may beprovided to a user equipment by a base station after RRC connectionprocedure. In this case, the RRC connection may mean that a radioresource is allocated to a user equipment based on RRC signalingexchanged between an RRC layer of the user equipment and a network viaSRB. After completion of the RRC connection procedure between the userequipment and the base station, the user equipment may be provided bythe base station with the setting information on the primary componentcarrier and the secondary component carrier. The setting information onthe secondary component carrier may include addition/deletion (oractivation/deactivation) of the secondary component carrier. Therefore,in order to activate a secondary component carrier between a basestation and a user equipment or deactivate a previous secondarycomponent carrier, it may be necessary to perform an exchange of RRCsignaling and MAC control element.

The configured set of serving cells for a UE therefore always consistsof one PCell and one or more SCells:

-   -   For each SCell the usage of uplink resources by the UE in        addition to the downlink ones is configurable (the number of DL        SCCs configured is therefore always larger than or equal to the        number of UL SCCs and no SCell can be configured for usage of        uplink resources only);    -   From a UE viewpoint, each uplink resource only belongs to one        serving cell;    -   The number of serving cells that can be configured depends on        the aggregation capability of the UE;    -   PCell can only be changed with handover procedure (i.e. with        security key change and RACH procedure);    -   PCell is used for transmission of PUCCH;    -   Unlike SCells, PCell cannot be de-activated;    -   Re-establishment is triggered when PCell experiences RLF, not        when SCells experience RLF;    -   NAS information is taken from PCell.

The activation or deactivation of the secondary component carrier may bedetermined by a base station based on a quality of service (QoS), a loadcondition of carrier and other factors. And, the base station may beable to instruct a user equipment of secondary component carrier settingusing a control message including such information as an indication type(activation/deactivation) for DL/UL, a secondary component carrier listand the like.

The reconfiguration, addition and removal of SCells can be performed byRRC. At intra-LTE handover, RRC can also add, remove, or reconfigureSCells for usage with the target PCell. When adding a new SCell,dedicated RRC signalling is used for sending all required systeminformation of the SCell i.e. while in connected mode, UEs need notacquire broadcasted system information directly from the SCells.

FIG. 7 is a conceptual diagram for Dual Connectivity (DC) between aMaster Cell Group (MCS) and a Secondary Cell Group (SCG).

The Dual Connectivity (DC) means that the UE can be connected to both aMaster eNode-B (MeNB) and a Secondary eNode-B (SeNB) at the same time.The MCG is a group of serving cells associated with the MeNB, comprisingof a PCell and optionally one or more SCells. And the SCG is a group ofserving cells associated with the SeNB, comprising of the special SCelland optionally one or more SCells. The MeNB is an eNB which terminatesat least S1-MME (S1 for the control plane) and the SeNB is an eNB thatis providing additional radio resources for the UE but is not the MeNB.

The Dual Connectivity is a kind of carrier aggregation in that the UE isconfigured a plurality serving cells. However, unlike all serving cellssupporting carrier aggregation of FIG. 6 are served by a same eNB, allserving cells supporting dual connectivity of FIG. 7 are served bydifferent eNBs, respectively at same time. The different eNBs areconnected via non-ideal backhaul interface because the UE is connectedwith the different eNBs at same time.

With Dual Connectivity, some of the data radio bearers (DRBs) can beoffloaded to the SCG to provide high throughput while keeping schedulingradio bearers (SRBs) or other DRBs in the MCG to reduce the handoverpossibility. The MCG is operated by the MeNB via the frequency of f1,and the SCG is operated by the SeNB via the frequency of f2. Thefrequency f1 and f2 may be equal. The backhaul interface (BH) betweenthe MeNB and the SeNB is non-ideal (e.g. X2 interface), which means thatthere is considerable delay in the backhaul and therefore thecentralized scheduling in one node is not possible.

For SCG, the following principles are applied:

-   -   At least one cell in SCG has a configured UL CC and one of them,        named PSCell, is configured with PUCCH resources;    -   When SCG is configured, there is always at least one SCG bearer        or one Split bearer;    -   Upon detection of a physical layer problem or a random access        problem on PSCell, or the maximum number of RLC retransmissions        has been reached associated with the SCG, or upon detection of        an access problem on PSCell (T307 expiry) during SCG addition or        SCG change:    -   RRC connection Re-establishment procedure is not triggered;    -   All UL transmissions towards all cells of the SCG are stopped;    -   MeNB is informed by the UE of SCG failure type.    -   For split bearer, the DL data transfer over the MeNB is        maintained.    -   Only the RLC AM bearer can be configured for the split bearer;    -   Like PCell, PSCell cannot be de-activated;    -   PSCell can only be changed with SCG change (i.e. with security        key change and RACH procedure);    -   Neither direct bearer type change between Split bearer and SCG        bearer nor simultaneous configuration of SCG and Split bearer        are supported.

With respect to the interaction between MeNB and SeNB, the followingprinciples are applied:

-   -   The MeNB maintains the RRM measurement configuration of the UE        and may, e.g, based on received measurement reports or traffic        conditions or bearer types, decide to ask a SeNB to provide        additional resources (serving cells) for a UE.    -   Upon receiving the request from the MeNB, a SeNB may create the        container that will result in the configuration of additional        serving cells for the UE (or decide that it has no resource        available to do so).    -   For UE capability coordination, the MeNB provides (part of) the        AS configuration and the UE capabilities to the SeNB.    -   The MeNB and the SeNB exchange information about UE        configuration by means of RRC containers (inter-node messages)        carried in X2 messages.    -   The SeNB may initiate a reconfiguration of its existing serving        cells (e.g., PUCCH towards the SeNB).    -   The SeNB decides which cell is the PSCell within the SCG.    -   The MeNB does not change the content of the RRC configuration        provided by the SeNB.    -   In the case of the SCG addition and SCG SCell addition, the MeNB        may provide the latest measurement results for the SCG cell(s).    -   Both MeNB and SeNB know the SFN and subframe offset of each        other by OAM, e.g., for the purpose of DRX alignment and        identification of measurement gap.

When adding a new SCG SCell, dedicated RRC signalling is used forsending all required system information of the cell as for CA describedabove, except for the SFN acquired from MIB of the PSCell of SCG.

FIG. 8 is a diagram for MAC structure overview in a UE side.

The MAC layer handles logical-channel multiplexing, hybrid-ARQretransmissions, and uplink and downlink scheduling. It is alsoresponsible for multiplexing/demultiplexing data across multiplecomponent carriers when carrier aggregation is used.

The MAC provides services to the RLC in the form of logical channels. Alogical channel is defined by the type of information it carries and isgenerally classified as a control channel, used for transmission ofcontrol and configuration information necessary for operating an LTEsystem, or as a traffic channel, used for the user data. The set oflogical-channel types specified for LTE includes:

-   -   The Broadcast Control Channel (BCCH), used for transmission of        system information from the network to all terminals in a cell.        Prior to accessing the system, a terminal needs to acquire the        system information to find out how the system is configured and,        in general, how to behave properly within a cell.    -   The Paging Control Channel (PCCH), used for paging of terminals        whose location on a cell level is not known to the network. The        paging message therefore needs to be transmitted in multiple        cells.    -   The Common Control Channel (CCCH), used for transmission of        control information in conjunction with random access.    -   The Dedicated Control Channel (DCCH), used for transmission of        control information to/from a terminal. This channel is used for        individual configuration of terminals such as different handover        messages.    -   The Multicast Control Channel (MCCH), used for transmission of        control information required for reception of the MTCH.    -   The Dedicated Traffic Channel (DTCH), used for transmission of        user data to/from a terminal. This is the logical channel type        used for transmission of all uplink and non-MBSFN downlink user        data.    -   The Multicast Traffic Channel (MTCH), used for downlink        transmission of MBMS services.

From the physical layer, the MAC layer uses services in the form oftransport channels. A transport channel is defined by how and with whatcharacteristics the information is transmitted over the radio interface.Data on a transport channel is organized into transport blocks. In eachTransmission Time Interval (TTI), at most one transport block of dynamicsize is transmitted over the radio interface to/from a terminal in theabsence of spatial multiplexing. In the case of spatial multiplexing(MIMO), there can be up to two transport blocks per TTI.

Associated with each transport block is a Transport Format (TF),specifying how the transport block is to be transmitted over the radiointerface. The transport format includes information about thetransport-block size, the modulation-and-coding scheme, and the antennamapping. By varying the transport format, the MAC layer can thus realizedifferent data rates. Rate control is therefore also known astransport-format selection.

The following transport-channel types are defined for LTE:

-   -   The Broadcast Channel (BCH) has a fixed transport format,        provided by the specifications. It is used for transmission of        parts of the BCCH system information, more specifically the        so-called Master Information Block (MIB).

The Paging Channel (PCH) is used for transmission of paging informationfrom the PCCH logical channel. The PCH supports discontinuous reception(DRX) to allow the terminal to save battery power by waking up toreceive the PCH only at predefined time instants. The Downlink SharedChannel (DL-SCH) is the main transport channel used for transmission ofdownlink data in LTE. It supports key LTE features such as dynamic rateadaptation and channel-dependent scheduling in the time and frequencydomains, hybrid ARQ with soft combining, and spatial multiplexing. Italso supports DRX to reduce terminal power consumption while stillproviding an always-on experience. The DL-SCH is also used fortransmission of the parts of the BCCH system information not mapped tothe BCH. There can be multiple DL-SCHs in a cell, one per terminalscheduled in this TTI, and, in some subframes, one DL-SCH carryingsystem information.

-   -   The Multicast Channel (MCH) is used to support MBMS. It is        characterized by a semi-static transport format and semi-static        scheduling. In the case of multi-cell transmission using MBSFN,        the scheduling and transport format configuration is coordinated        among the transmission points involved in the MBSFN        transmission.    -   The Uplink Shared Channel (UL-SCH) is the uplink counterpart to        the DL-SCH?that is, the uplink transport channel used for        transmission of uplink data.

In addition, the Random-Access Channel (RACH) is also defined as atransport channel, although it does not carry transport blocks.

To support priority handling, multiple logical channels, where eachlogical channel has its own RLC entity, can be multiplexed into onetransport channel by the MAC layer. At the receiver, the MAC layerhandles the corresponding demultiplexing and forwards the RLC PDUs totheir respective RLC entity for in-sequence delivery and the otherfunctions handled by the RLC. To support the demultiplexing at thereceiver, a MAC is used. To each RLC PDU, there is an associatedsub-header in the MAC header. The sub-header contains the identity ofthe logical channel (LCID) from which the RLC PDU originated and thelength of the PDU in bytes. There is also a flag indicating whether thisis the last sub-header or not. One or several RLC PDUs, together withthe MAC header and, if necessary, padding to meet the scheduledtransport-block size, form one transport block which is forwarded to thephysical layer.

In addition to multiplexing of different logical channels, the MAC layercan also insert the so-called MAC control elements into the transportblocks to be transmitted over the transport channels. A MAC controlelement is used for inband control signaling?for example, timing-advancecommands and random-access response. Control elements are identifiedwith reserved values in the LCID field, where the LCID value indicatesthe type of control information.

Furthermore, the length field in the sub-header is removed for controlelements with a fixed length.

The MAC multiplexing functionality is also responsible for handling ofmultiple component carriers in the case of carrier aggregation. Thebasic principle for carrier aggregation is independent processing of thecomponent carriers in the physical layer, including control signaling,scheduling and hybrid-ARQ retransmissions, while carrier aggregation isinvisible to RLC and PDCP. Carrier aggregation is therefore mainly seenin the MAC layer, where logical channels, including any MAC controlelements, are multiplexed to form one (two in the case of spatialmultiplexing) transport block(s) per component carrier with eachcomponent carrier having its own hybrid-ARQ entity.

In Dual Connectivity, two MAC entities are configured in the UE: one forthe MCG and one for the SCG. Each MAC entity is configured by RRC with aserving cell supporting PUCCH transmission and contention based RandomAccess. In this specification, the term SpCell refers to such cell,whereas the term SCell refers to other serving cells. The term SpCelleither refers to the PCell of the MCG or the PSCell of the SCG dependingon if the MAC entity is associated to the MCG or the SCG, respectively.A Timing Advance Group containing the SpCell of a MAC entity is referredto as pTAG, whereas the term sTAG refers to other TAGs.

If a reset of the MAC entity is requested by upper layers, the MACentity shall:

-   -   initialize Bj for each logical channel to zero;    -   stop (if running) all timers;    -   consider all timeAlignmentTimers as expired;    -   set the NDIs for all uplink HARQ processes to the value 0;    -   stop, if any, ongoing RACH procedure;    -   discard explicitly signalled ra-PreambleIndex and        ra-PRACH-MaskIndex, if any;    -   flush Msg3 buffer;    -   cancel, if any, triggered Scheduling Request procedure;    -   cancel, if any, triggered Buffer Status Reporting procedure;    -   cancel, if any, triggered Power Headroom Reporting procedure;    -   flush the soft buffers for all DL HARQ processes;    -   for each DL HARQ process, consider the next received        transmission for a TB as the very first transmission;    -   release, if any, Temporary C-RNTI.

FIG. 9 is a diagram for an activation/deactivation MAC control element.

If the UE is configured with one or more SCells, the network mayactivate and deactivate the configured SCells. The PCell is alwaysactivated. The network activates and deactivates the SCell(s) by sendingthe Activation/Deactivation MAC control element. Furthermore, the UEmaintains a sCellDeactivationTimer timer per configured SCell anddeactivates the associated SCell upon its expiry. The same initial timervalue applies to each instance of the sCellDeactivationTimer and it isconfigured by RRC. The configured SCells are initially deactivated uponaddition and after a handover.

The UE configures each SCell to each TTI and for each configured SCell:

If the UE receives an Activation/Deactivation MAC control element inthis TTI activating the SCell, the UE may activate the SCell in the TTI.The UE can apply normal SCell operation including i) SRS transmissionson the SCell, ii) CQI/PMI/RI/PTI reporting for the SCell, iii) PDCCHmonitoring on the SCell, or iv) PDCCH monitoring for the SCell. Also theUE may start or restart the sCellDeactivationTimer associated with theSCell and trigger PHR.

If the UE receives an Activation/Deactivation MAC control element inthis TTI deactivating the SCell, or if the sCellDeactivationTimerassociated with the activated SCell expires in this TTI, the UE candeactivate the SCell in the TTI, stop the sCellDeactivationTimerassociated with the SCell, and flush all HARQ buffers associated withthe SCell.

If PDCCH on the activated SCell indicates an uplink grant or downlinkassignment; or if PDCCH on the Serving Cell scheduling the activatedSCell indicates an uplink grant or a downlink assignment for theactivated SCell, the UE can restart the sCellDeactivationTimerassociated with the SCell.

If the SCell is deactivated, the UE will not transmit SRS on the SCell,transmit on UL-SCH on the SCell, transmit on RACH on the SCell, monitorthe PDCCH on the SCell, or monitor the PDCCH for the SCell.

HARQ feedback for the MAC PDU containing Activation/Deactivation MACcontrol element may not be impacted by PCell interruption due to SCellactivation/deactivation.

The Activation/Deactivation MAC control element is identified by a MACPDU subheader with LCID as specified in table 1. It has a fixed size andconsists of a single octet containing seven C-fields and one R-field.The Activation/Deactivation MAC control element is defined as FIG. 9.

TABLE 1 Index LCID values 00000 CCCH 00001-01010 Identity of the logicalchannel 01011-11001 Reserved 11010 Long DRX Command 11011Activation/Deactivation 11100 UE Contention Resolution Identity 11101Timing Advance Command 11110 DRX Command 11111 Padding

Ci field indicates the activation/deactivation status of the SCell withSCellIndex i, if there is an SCell configured with SCellIndex i. Else,the UE may ignore the Ci field. The Ci field is set to “1” to indicatethat the SCell with SCellIndex i shall be activated. The Ci field is setto “0” to indicate that the SCell with SCellIndex i shall bedeactivated. R field is a reserved bit, and set to ‘0’.

The sCellDeactivationTimer is a SCell deactivation timer. Value innumber of radio frames. Value rf4 corresponds to 4 radio frames, valuerf8 corresponds to 8 radio frames and so on. E-UTRAN only configures thefield if the UE is configured with one or more SCells other than thePSCell. If the field is absent, the UE shall delete any existing valuefor this field and assume the value to be set to infinity. The samevalue applies for each SCell of a Cell Group (i.e. MCG or SCG) (althoughthe associated functionality is performed independently for each SCell).

FIG. 10 is a diagram for signaling of buffer status and power-headroomreports.

The scheduler needs knowledge about the amount of data awaitingtransmission from the terminals to assign the proper amount of uplinkresources. Obviously, there is no need to provide uplink resources to aterminal with no data to transmit as this would only result in theterminal performing padding to fill up the granted resources. Hence, asa minimum, the scheduler needs to know whether the terminal has data totransmit and should be given a grant. This is known as a schedulingrequest.

The use of a single bit for the scheduling request is motivated by thedesire to keep the uplink overhead small, as a multi-bit schedulingrequest would come at a higher cost. A consequence of the single bitscheduling request is the limited knowledge at the eNodeB about thebuffer situation at the terminal when receiving such a request.Different scheduler implementations handle this differently. Onepossibility is to assign a small amount of resources to ensure that theterminal can exploit them efficiently without becoming power limited.Once the terminal has started to transmit on the UL-SCH, more detailedinformation about the buffer status and power headroom can be providedthrough the inband MAC control message, as discussed below.

Terminals that already have a valid grant obviously do not need torequest uplink resources. However, to allow the scheduler to determinethe amount of resources to grant to each terminal in future subframes,information about the buffer situation and the power availability isuseful, as discussed above. This information is provided to thescheduler as part of the uplink transmission through MAC controlelement. The LCID field in one of the MAC subheaders is set to areserved value indicating the presence of a buffer status report, asillustrated in FIG. 10.

Especially, to assist the scheduler in the selection of a combination ofmodulation-and-coding scheme and resource size M that does not lead tothe terminal being power limited, the terminal can be configured toprovide regular power headroom reports on its power usage. There is aseparate transmit-power limitation for each component carrier. Thus,power headroom should be measured and reported separately for eachcomponent carrier.

There are two different Types of power-headroom reports defined for LTErelease 10, Type 1 and Type 2. Type 1 reporting reflects the powerheadroom assuming PUSCH-only transmission on the carrier, while the Type2 report assumes combined PUSCH and PUCCH transmission.

The Type1 power headroom valid for a certain subframe, assuming that theterminal was really scheduled for PUSCH transmission in that subframe,is given by the following expression:Power Headroom=P _(CMAX,c)−(P _(α,PUSCH) +α·PL_(DL)+10·log₁₀(M)+Δ_(MCS)+δ).  [Equation 1]

Where the values for M and ΔMCS correspond to the resource assignmentand modulation-and-coding scheme used in the subframe to which thepower-headroom report corresponds. It can be noted that the powerheadroom is not a measure of the difference between the maximumper-carrier transmit power and the actual carrier transmit power. It canbe seen that the power headroom is a measure of the difference betweenPCMAX,c and the transmit power that would have been used assuming thatthere would have been no upper limit on the transmit power. Thus, thepower headroom can very well be negative. More exactly, a negative powerheadroom indicates that the per-carrier transmit power was limited byPCMAX,c at the time of the power headroom reporting. As the networkknows what modulation-and-coding scheme and resource size the terminalused for transmission in the subframe to which the power-headroom reportcorresponds, it can determine what are the valid combinations ofmodulation-and-coding scheme and resource size M, assuming that thedownlink path loss PLDL and the term δ have not changed substantially.

Type-1 power headroom can also be reported for subframes where there isno actual PUSCH transmission. In such cases, 10 log 10 (M) and ΔMCS inthe expression above are set to zero:Power Headroom=P _(CMAX,c)−(P _(0,PUSCH) +α·PL_(DL)+δ)·Δ_(MCS)+δ).  [Equation 2]

This can be seen as the power headroom assuming a default transmissionconfiguration corresponding to the minimum possible resource assignment(M=1) and the modulation-and-coding scheme associated with ΔMCS=0 dB.

Similarly, Type 2 power headroom reporting is defined as the differencebetween the maximum per-carrier transmit power and the sum of the PUSCHand PUCCH transmit power respectively, once again not taking intoaccount any maximum per-carrier power when calculating the PUSCH andPUCCH transmit power.

Similar to Type 1 power headroom reporting, the Type 2 power headroomcan also be reported for subframes in which no PUSCH and/or PUCCH istransmitted. In that case a virtual PUSCH and or PUCCH transmit power iscalculated, assuming the smallest possible resource assignment (M=1) andΔMCS=0 dB for PUSCH and ΔFormat=0 for PUCCH.

For the uplink, the power availability, or power headroom is defined asthe difference between the nominal maximum output power and theestimated output power for UL-SCH transmission. This quantity can bepositive as well as negative (on a dB scale), where a negative valuewould indicate that the network has scheduled a higher data rate thanthe terminal can support given its current power availability. The powerheadroom depends on the power-control mechanism and thereby indirectlyon factors such as the interference in the system and the distance tothe base stations.

Information about the power headroom is fed back from the terminals tothe eNodeB in a similar way as the buffer-status reports?that is, onlywhen the terminal is scheduled to transmit on the UL-SCH. Type 1 reportsare provided for all component carriers simultaneously, while Type 2reports are provided for the primary component carrier only.

A power headroom report can be triggered for the following reasons: i)periodically as controlled by a timer, ii) change in path loss, sincethe last power headroom report is larger than a (configurable)threshold, and iii) instead of padding (for the same reason asbuffer-status reports).

It is also possible to configure a prohibit timer to control the minimumtime between two power-headroom reports and thereby the signaling loadon the uplink.

The Power Headroom reporting procedure is used to provide the servingeNB with information about the difference between the nominal UE maximumtransmit power and the estimated power for UL-SCH transmission peractivated Serving Cell and also with information about the differencebetween the nominal UE maximum power and the estimated power for UL-SCHand PUCCH transmission on SpCell.

RRC controls Power Headroom reporting by configuring the two timersperiodicPHR-Timer and prohibitPHR-Timer, and by signallingdl-PathlossChange which sets the change in measured downlink pathlossand the required power backoff due to power management to trigger a PHR.

A Power Headroom Report (PHR) shall be triggered if any of the followingevents occur: i) prohibitPHR-Timer expires or has expired and the pathloss has changed more than dl-PathlossChange dB for at least oneactivated Serving Cell of any MAC entity which is used as a pathlossreference since the last transmission of a PHR in this MAC entity whenthe MAC entity has UL resources for new transmission; ii)periodicPHR-Timer expires; iii) upon configuration or reconfiguration ofthe power headroom reporting functionality by upper layers, which is notused to disable the function; iv) activation of an SCell of any MACentity with configured uplink, v) addition of the PSCell, vi)prohibitPHR-Timer expires or has expired, when the MAC entity has ULresources for new transmission, and the following is true in this TTIfor any of the activated Serving Cells of any MAC entity with configureduplink: there are UL resources allocated for transmission or there is aPUCCH transmission on this cell, and the required power backoff due topower management for this cell has changed more than dl-PathlossChangedB since the last transmission of a PHR when the MAC entity had ULresources allocated for transmission or PUCCH transmission on this cell.

If the MAC entity has UL resources allocated for new transmission forthis TTI, and if it is the first UL resource allocated for a newtransmission since the last MAC reset, the MAC entity shall startperiodicPHR-Timer.

If the MAC entity has UL resources allocated for new transmission forthis TTI, and if the Power Headroom reporting procedure determines thatat least one PHR has been triggered and not cancelled, and, if theallocated UL resources can accommodate a PHR MAC control element plusits subheader if neither extendedPHR nor dualConnectivityPHR isconfigured, or the Extended PHR MAC control element plus its subheaderif extendedPHR is configured, or the Dual Connectivity PHR MAC controlelement plus its subheader if dualConnectivityPHR is configured, as aresult of logical channel prioritization, the MAC entity shall start orrestart periodicPHR-Timerm or start or restart prohibitPHR-Timer, orcancel all triggered PHR(s).

If extendedPHR is configured, the MAC entity shall obtain the value ofthe Type 1 power headroom for each activated Serving Cell withconfigured uplink, and the MAC entity shall the value for thecorresponding PCMAX,c field from the physical layer, if the MAC entityhas UL resources allocated for transmission on this Serving Cell forthis TTI.

Else if dualConnectivityPHR is configured, the MAC entity shall obtainthe value of the Type 1 power headroom for each activated Serving Cellwith configured uplink associated with any MAC entity. If this MACentity has UL resources allocated for transmission on this Serving Cellfor this TTI or if the other MAC entity has UL resources allocated fortransmission on this Serving Cell for this TTI and phr-ModeOtherCG isset to real by higher layers, the MAC entity shall obtain the value forthe corresponding PCMAX,c field from the physical layer.

Else the MAC entity shall obtain the value of the Type 1 power headroomfrom the physical layer, and instruct the Multiplexing and Assemblyprocedure to generate and transmit a PHR MAC control element based onthe value reported by the physical layer.

In the prior art, the UE triggers PHR when a SCell with configureduplink is activated. The reason to trigger PHR in this case is that whena SCell with configured uplink is activated, the uplink power headroomof the UE is very likely to be changed, so the reporting of the changeduplink power headroom is time-critical for the eNB scheduler not torequire more power than available in the UE.

In Rel-13, cells other than the special cell (i.e. PCell or PSCell)could be configured with PUCCH resource in order to offload the PUCCHtraffic from the special cell to other cells. The SCell configured withPUCCH is assumed to be always activated similar to the special cell.

According to the prior art, when the PUCCH is deconfigured from theSCell, the UE does not trigger PHR. However, deconfiguring PUCCH fromthe SCell means that the control information, e.g. HARQ feedback, istransmitted by PUCCH of other cells. This means that, even though the UEoverall power situation is not much changed, per-cell power situationwould be much changed. Therefore, reporting power situation to the eNBscheduler is also important when the PUCCH is deconfigured from a SCell.

FIG. 11 is a conceptual diagram for de-configuring a SCell from PUCCHresource in a carrier aggregation system according to embodiments of thepresent invention.

In this invention, a UE, configured with at least one SCell with PUCCHresource, triggers a PHR when the PUCCH resource is deconfigured fromone of the SCell. The PHR includes power headroom information of eachactivated cell in the UE.

The UE configures with at least one SCell other than special cell, wherethe SCell is configured with PUCCH resource (S1101).

During the time while the PUCCH resource is configured for the SCell,the UE considers that the SCell is in an activated state. I.e., the UEdisables the sCellDeactivationTimer associated with the SCell for whichthe PUCCH resource is configured, or the UE sets thesCellDeactivationTimer associated with the SCell for which the PUCCHresource is configured to infinity.

When the UE receives a signaling indicating that the PUCCH resource isde-configured from the SCell with the PUCCH resource (S1103), the UEde-configures the PUCCH resource from the SCell according to thesignaling (S1105), and triggers PHR when the PUCCH resource isde-configured from the SCell (S1107).

Preferably, the network transmits the signaling in order to de-configurethe PUCCH resource of the cell via an RRC signaling or MAC signaling,including: an indication of at least one cell, or an indication of PUCCHresource de-configuration of the at least one cell, orsCellDeactivationTimer value of at least one cell.

Preferably, the UE generates PHR by including power headroom informationof each activated cell in the UE. The UE then sends the generated PHR tothe eNB (S1109).

Preferably, the UE triggers the PHR, if the SCell is in activate statewhen the PUCCH resource is deconfigured from the SCell.

Preferably, The UE triggers the PHR, if the SCell is in activate stateafter the PUCCH resource is deconfigured from the SCell.

In addition, the SCell from which the PUCCH resource is de-configured iseither activated or deactivated after the PUCCH de-configurationdepending on configuration.

For example, a UE is configured with PCell, SCell1 and SCell2.

As PCell is a special cell, it is always configured with PUCCH. TheSCell1 is also configured with PUCCH. The SCell2 is not configured withPUCCH.

The UE receives a reconfiguration message from the eNB which indicatesdeconfiguration of PUCCH from the SCell1. The UE deconfigures PUCCH fromthe SCell1, triggers a PHR, and transmits the PHR to the eNB.

With Dual Connectivity, the UE can have multiple MAC entities, i.e. onefor MeNB and the other for SeNB. In this case, there are two options totrigger PHR when the PUCCH is deconfigured from a SCell: i) the UEtriggers PHR in both MAC entities and transmits PHR to both eNBs, or ii)the UE triggers PHR in only the MAC entity to which the PUCCHdeconfigured SCell belongs.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term eNB′ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

While the above-described method has been described centering on anexample applied to the 3GPP LTE system, the present invention isapplicable to a variety of wireless communication systems in addition tothe 3GPP LTE system.

What is claimed is:
 1. A method for a User Equipment (UE) operating in awireless communication system, the method comprising: configuring aSecondary Cell (SCell) with Physical Uplink Control Channel (PUCCH)resource; receiving a signaling indicating that the PUCCH resource isde-configured from the SCell; de-configuring the PUCCH resource from theSCell according to the signaling; and triggering a Power HeadroomReporting (PHR) when the PUCCH resource is de-configured from the SCell.2. The method according to claim 1, wherein when the PUCCH resource isde-configured from the SCell, if the SCell is in activate state, the UEtriggers the PHR.
 3. The method according to claim 1, wherein after thePUCCH resource is de-configured from the SCell, if the SCell is inactivate state, the UE triggers the PHR.
 4. The method according toclaim 1, wherein the signaling indicating that the PUCCH resource isde-configured from the SCell including at least one of: an indication ofthe SCell from which the PUCCH resource is de-configured; an indicationof PUCCH resource de-configuration of the SCell from which the PUCCHresource is de-configured.
 5. The method according to claim 1, whereinthe signaling is received via a Radio Resource Control (RRC) or a MediumAccess Control (MAC) signaling.
 6. The method according to claim 1,wherein the SCell from which the PUCCH resource is de-configured iseither activated or deactivated after the PUCCH de-configurationdepending on configuration.
 7. The method according to claim 1, furthercomprising: transmitting the triggered PHR to a base station.
 8. A UserEquipment (UE) operating in a wireless communication system, the UEcomprising: a Radio Frequency (RF) module; and a processor configured tocontrol the RF module, wherein the processor is configured to configurea Secondary Cell (SCell) with Physical Uplink Control Channel (PUCCH)resource, to receive a signaling indicating that the PUCCH resource isde-configured from the SCell, to de-configure the PUCCH resource fromthe SCell according to the signaling, and to trigger a Power HeadroomReporting (PHR) when the PUCCH resource is de-configured from the SCell.9. The UE according to claim 8, wherein when the PUCCH resource isde-configured from the SCell, if the SCell is in activate state, theprocessor triggers the PHR.
 10. The UE according to claim 8, whereinafter the PUCCH resource is de-configured from the SCell, if the SCellis in activate state, the processor triggers the PHR.
 11. The UEaccording to claim 8, wherein the signaling indicating that the PUCCHresource is de-configured from the SCell including at least one of: anindication of the SCell from which the PUCCH resource is de-configured;an indication of PUCCH resource de-configuration of the SCell from whichthe PUCCH resource is de-configured.
 12. The UE according to claim 8,wherein the signaling is received via a Radio Resource Control (RRC) ora Medium Access Control (MAC) signaling.
 13. The UE according to claim8, wherein the SCell from which the PUCCH resource is de-configured iseither activated or deactivated after the PUCCH de-configurationdepending on configuration.
 14. The UE according to claim 8, wherein theprocessor is further configured to transmit the triggered PHR to a basestation.